My taxable social security doesn't match the What If MFS worksheet

[AndreaG]

One reason for this might be because of the filing status. When you file married filing separately and you lived together with your spouse at any time during the year, you must include in income, a greater percentage of your social security benefits. Please refer to line item #8 on page 8 of pub 501 for additional clarification. https://www.irs.gov/pub/irs-pdf/p501.pdf

If this answer does NOT fit your situation, please provide me with more details so that I can better address your concerns.